LC8 enhances 53BP1 foci through heterogeneous bridging of 53BP1 oligomers

  1. Jesse Howe
  2. Douglas Walker
  3. Kyle Tengler
  4. Maya Sonpatki
  5. Patrick N Reardon
  6. Justin WC Leung
  7. Elisar J Barbar  Is a corresponding author
  1. Oregon State University, United States
  2. The University of Texas Health Science Center at San Antonio, United States

Abstract

53BP1 is a key player in DNA repair and together with BRCA1 regulate selection of DNA double strand break repair mechanisms. Localization of DNA repair factors to sites of DNA damage by 53BP1 is controlled by its oligomerization domain (OD) and binding to LC8, a hub protein that functions to dimerize >100 clients. Here we show that 53BP1 OD is a trimer, an unusual finding for LC8 clients which are all dimers or tetramers. As a trimer, 53BP1 forms a heterogeneous mixture of complexes when bound to dimeric LC8 with the largest mass corresponding to a dimer-of-trimers bridged by 3 LC8 dimers. Analytical ultracentrifugation and isothermal titration calorimetry demonstrate that only the second of the three LC8 recognition motifs is necessary for a stable bridged complex. The stability of the bridged complex is tuned by multivalency, binding specificity of the second LC8 site, and the length of the linker separating the LC8 binding domain and OD. 53BP1 mutants deficient in bridged species fail to impact 53BP1 focus formation in human cell culture studies, suggesting that the primary role of LC8 is to bridge 53BP1 trimers which in turn promotes recruitment of 53BP1 at sites of DNA damage. We propose that the formation of higher-order oligomers of 53BP1 explains how LC8 elicits an improvement in 53BP1 foci and affects the structure and functions of 53BP1.

Data availability

All data generated or analysed during this study are included in the manuscript; source data files have been provided for Figures 1-4, 6-7

Article and author information

Author details

  1. Jesse Howe

    Department of Biochemistry and Biophysics, Oregon State University, Corvallis, United States
    Competing interests
    The authors declare that no competing interests exist.
  2. Douglas Walker

    Department of Biochemistry and Biophysics, Oregon State University, Corvallis, United States
    Competing interests
    The authors declare that no competing interests exist.
  3. Kyle Tengler

    Department of Radiation Oncology, The University of Texas Health Science Center at San Antonio, San Antonio, United States
    Competing interests
    The authors declare that no competing interests exist.
  4. Maya Sonpatki

    Department of Biochemistry and Biophysics, Oregon State University, Corvallis, United States
    Competing interests
    The authors declare that no competing interests exist.
  5. Patrick N Reardon

    Oregon State University NMR Facility, Oregon State University, Corvallis, United States
    Competing interests
    The authors declare that no competing interests exist.
  6. Justin WC Leung

    Department of Radiation Oncology, The University of Texas Health Science Center at San Antonio, San Antonio, United States
    Competing interests
    The authors declare that no competing interests exist.
  7. Elisar J Barbar

    Department of Biochemistry and Biophysics, Oregon State University, Corvallis, United States
    For correspondence
    Elisar.Barbar@oregonstate.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-4892-5259

Funding

National Institute of General Medical Sciences (R01GM141733)

  • Elisar J Barbar

National Institute of General Medical Sciences (R35GM137798)

  • Justin WC Leung

National Cancer Institute (R01CA244261)

  • Justin WC Leung

American Cancer Society (RSG-20-131-01-DMC)

  • Justin WC Leung

ARCS Oregon Chapter (Graduate Student Fellowship)

  • Jesse Howe

National Institute of Health (1S10OD018518)

  • Elisar J Barbar

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Copyright

© 2025, Howe et al.

This article is distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use and redistribution provided that the original author and source are credited.

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  1. Jesse Howe
  2. Douglas Walker
  3. Kyle Tengler
  4. Maya Sonpatki
  5. Patrick N Reardon
  6. Justin WC Leung
  7. Elisar J Barbar
(2025)
LC8 enhances 53BP1 foci through heterogeneous bridging of 53BP1 oligomers
eLife 14:e102179.
https://doi.org/10.7554/eLife.102179

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https://doi.org/10.7554/eLife.102179